Cerebral edema in both the human and experimental animal will be studied by means of axial computerized tomography using the EMI scanner. Tissue densities as determined by this technique will be correlated with histologic patterns and chemical changes in the brain. The experimental studies will involve cryogenic cerebral injury in the rhesus monkey. The x-ray attenuation of pure chemical substances and solutions will also be studied in a phantom. Information obtained from these studies will be used to interpret chemical changes occurring in the brain in pathological conditions in relation to changes in the EMI scan. From these studies, we hope to be able to define a method for quantifying cerebral edema in the living patient using the EMI scanner.